Yahoo Acess Token Generation Failed

Hey there! I set this up many months ago on a site hosted on Site5, and it worked brilliantly until lately. It now is giving an error message:

[Access token generation failed(ACCESS_TOKEN_GENERATION_FAILED)]

I tried setting it all up again from scratch, and still got the error.

I tried running the Connectivity test, and got this message:
“No outbound route between this site and the Internet on Port 25.”

I read the suggestions below it but none of them seem to apply.

The diagnostic test gave me:

OS: Linux judith.accountservergroup.com 3.14.25-grsec.3.el5 #1 SMP Thu Apr 2 14:45:16 UTC 2015 x86_64
PHP: Linux 5.3.29 C
PHP Dependencies: iconv=Yes, spl_autoload=Yes, openssl=Yes, sockets=Yes, allow_url_fopen=Yes, mcrypt=Yes, zlib_encode=Yes
WordPress: 4.3.1 en_US UTF-8
WordPress Theme: Christine Hayes
WordPress Plugins: Gravity Forms, Advanced Custom Fields: Options Page, Advanced Custom Fields: Repeater Field, Advanced Custom Fields, BackupBuddy, FooBox HTML & Media Lightbox, Login LockDown, Postman SMTP, Simple Image Sizes, Sucuri Security – Auditing, Malware Scanner and Hardening, Yoast SEO
WordPress wp_mail Filter(s): wp_staticize_emoji_for_email
Postman: 1.7.2
Postman Sender Domain (Envelope|Message): yahoo.com | yahoo.com
Postman Prevent Message Sender Override (Email|Name): No | No
Postman Active Transport: Default (smtp:none:none://localhost:25)
Postman Active Transport Status (Ready|Connected): No | Yes
Postman Selected Transport: SMTP (smtp:tls:oauth2://smtp.mail.yahoo.com:587)
Postman Selected Transport Status (Ready|Connected): No | Yes
Postman Deliveries (Success|Fail): 12 | 7

https://ww.wp.xz.cn/plugins/postman-smtp/